Project Summary The purpose of the proposed work is first-in-man testing of novel painless defibrillation (PaDe) therapy. Sudden cardiac arrest (SCA) remains the number one killer in western civilization. The underlying mechanism of SCA is usually ventricular fibrillation (VF), and survival depends on prompt defibrillation. Existing defibrillators rely on the delivery of a brief high voltage shock to the heart. While this is life-saving, the shock is extremely painful when delivered to a conscious patient, as typically happens when the therapy is provided by an ICD. The pain caused by standard ICD shocks is due to the abrupt contraction of skeletal muscles of the chest and abdomen when the shock is applied to the heart. Our team has developed a novel means to accomplish painless defibrillation using a burst of high frequency alternating current to tetanize skeletal muscle so it does not further contract when a defibrillatory shock is then applied. We have already proven substantial reduction in skeletal muscle activation in animals defibrillated using this technology, and therefore believe that delivery of this novel therapy in humans will be a far less painful alternative to standard defibrillation shocks. In the proposed work, a table-top PaDe system developed in our Phase II grant will undergo final verification and validation testing needed to obtain FDA approval of an IDE, which will then enable us to evaluate this therapy in patients coming for elective ICD replacement. Patients will receive one PaDe therapy and one standard shock in random order, and will report the pain perceived with each of these, blinded to which is which. We intend to show that PaDe therapy is safe and effective, and will then seek FDA approval of the therapy.